Because Batman is so successful, well-known, and been around for so long, I feel like he's the one comicbook character that can have villains show up in a film and not need introductions or origins... especially after Nolan's trilogy.

I think the next Batman movie should be more like Arkham City... where several villains (Joker, Riddler, Two-Face, etc) all play a role in a huge criminal plot and Batman battles all of them. Even the common filmgoer will know who these characters are and not need an origin story for them...